Solid-phase extraction is a method to separate a measurement component(s) and an impurity(ies) in a sample solution from each other based on physical and chemical properties by using a solid substance (solid-phase extraction material) generally referred to as a solid phase. The solid-phase extraction is used for removing the impurities, which disturb analysis in various analysis techniques (liquid chromatograph, mass analysis), to purify the measurement component.
Examples of the sample used in the analysis include urine, blood, water, and soil. If the affinity between a measurement component and the surface of the solid-phase extraction material is high when the sample solution passes through the solid-phase extraction material, the measurement component of the sample solution is selectively adsorbed. Therefore, purification or condensing of the measurement component can be carried out.
As the solid-phase extraction material, generally, particles of organic polymers such as silica gel and styrene-divinylbenzene copolymer or the particles thereof of which surfaces are chemically modified are used.
Steps of the solid-phase extraction are composed of three steps: an adsorbing step in which the measurement component in the sample solution is adsorbed by the solid-phase extraction material, a cleaning step in which the impurities other than the measurement component adsorbed on the solid-phase extraction material are cleaned, and an eluting step in which the measurement component adsorbed on the solid-phase extraction material is eluted.
In the adsorbing step, the measurement component is adsorbed, and the components (impurities) which disturb analysis flow out without being adsorbed. This is a first purification step. However, since some impurities are adsorbed on the solid-phase extraction material, the adsorbed impurities are removed in the cleaning step. This is a second purification step.
In the eluting step, the purified measurement component is separated from the solid-phase extraction material by an eluting solution. The extracted solution after the separation is sent to an analysis apparatus, and the signal intensity of the measurement component is measured. As described above, in the solid-phase extraction, the impurities are removed in the order of the adsorbing, cleaning, and eluting steps, thereby purifying the measurement component.
Examples of the solid-phase extraction apparatus that automatically carries out above-described three steps include: a solid-phase extraction apparatus described in Japanese Patent Application Laid-Open Publication No. H08-164302 (Patent Document 1) that applies a pressure to a sample solution by using a pressurizing mechanism to cause the solution to pass through a solid-phase extraction material and a solid-phase extraction apparatus described in Japanese Patent Application Laid-Open Publication No. 2006-7081 (Patent Document 2) that causes a sample solution to pass through a solid-phase extraction material by using a depressurizing mechanism.
Examples of a different pressurizing-type extraction apparatus include an extraction apparatus described in Japanese Patent Application Laid-Open Publication No. 2005-110670 (Patent Document 3) that determines pressurization condition in accordance with the information corresponding to the type of a sample solution in advance.